345 research outputs found

### Vafa-Witten theorem, vector meson condensates and magnetic-field-induced electromagnetic superconductivity of vacuum

We show that the electromagnetic superconductivity of vacuum in strong
magnetic field background is consistent with the Vafa-Witten theorem because
the charged vector meson condensates lock relevant internal global symmetries
of QCD with the electromagnetic gauge group.Comment: 2 page

### Gluodynamics in External Field: A Test of the Dual Superconductor Picture

We study gluodynamics in an external Abelian electromagnetic field within the
dual superconductor approach. We show that the SU(2) gluodynamics should
possess a deconfining phase transition at zero temperature at certain value of
the external field. A dual superconductor model for the SU(3) gauge theory in
external field predicts a rich phase structure containing confinement,
asymmetric confinement and deconfinement phases. These results can be used to
check the validity of the dual superconductor description of gluodynamics in
external fields. We also discuss the gauge-independence of the obtained
results.Comment: Talk given at ``Confinement 2003'', RIKEN, Wako, Japan, July 21-24,
2003; 5 pages, 1 figure, uses ws-procs9x6.cl

### Permanently rotating devices: extracting rotation from quantum vacuum fluctuations?

We propose a set of devices of simple geometrical design which may exhibit a
permanent rotation due to quantum (vacuum) fluctuations. These objects - which
have no moving parts - impose certain boundary conditions on quantum
fluctuations thus affecting their vacuum energy similarly to the standard
Casimir effect. The boundary conditions are chosen in such a way that the
vacuum energy for a static device is larger compared to the energy of the
vacuum fluctuations in a state when the device rotates about a certain axis.
The optimal frequency of rotation is determined by geometry and moment of
inertia of the device. We illustrate our ideas in a vacuum of a massless scalar
field theory using simplest Dirichlet-type boundary conditions. We also propose
an experimental setup to verify the existence of the rotational vacuum effect.Comment: 5 pages, 8 figures; comments are welcom

### Comment on "Charged vector mesons in a strong magnetic field"

In a recent paper Y. Hidaka and A. Yamamoto [Phys. Rev. D 87 (2013) 094502]
claim -- using both analytical and numerical approaches -- that the charged rho
mesons cannot condense in the vacuum subjected to a strong magnetic field. In
this Comment we point out that both analytical and numerical results of this
paper are consistent with the inhomogeneous rho-meson condensation.
Furthermore, we show that the numerical results of the paper support the
presence of the expected (in quenched lattice QCD) crossover transition driven
by the rho-meson condensation. Finally, we stress that the inhomogeneous
rho-meson condensation is consistent with both Vafa-Witten and Elitzur
theorems.Comment: 4 pages, 4 figure

### Can nothing be a superconductor and a superfluid?

A superconductor is a material that conducts electric current with no
resistance. Superconductivity and magnetism are known to be antagonistic
phenomena: superconductors expel weak external magnetic field (the Meissner
effect) while a sufficiently strong magnetic field, in general, destroys
superconductivity. In a seemingly contradictory statement, we show that a very
strong magnetic field can turn an empty space into a superconductor. The
external magnetic field required for this effect should be about 10^{16} Tesla
(eB ~ 1 GeV^2). The physical mechanism of the exotic vacuum superconductivity
is as follows: in strong magnetic field the dynamics of virtual quarks and
antiquarks is effectively one-dimensional because these electrically charged
particles tend to move along the lines of the magnetic field. In one spatial
dimension a gluon-mediated attraction between a quark and an antiquark of
different flavors inevitably leads to formation of a colorless spin-triplet
bound state (a vector analogue of the Cooper pair) with quantum numbers of an
electrically charged rho meson. Such quark-antiquark pairs condense to form an
anisotropic inhomogeneous superconducting state similar to the Abrikosov vortex
lattice in a type-II superconductor. The onset of the superconductivity of the
charged rho mesons should also induce an inhomogeneous superfluidity of the
neutral rho mesons. The vacuum superconductivity should survive at very high
temperatures of typical Quantum Chromodynamics (QCD) scale of 10^{12} K (T ~
100 MeV). We propose the phase diagram of QCD in the plane "magnetic field -
temperature".Comment: 10 pages, 5 figures, contribution to the proceedings of the workshop
"The many faces of QCD", 2-5 November 2010, Gent, Belgiu

### Anomalous Transport Due to the Conformal Anomaly

We show that the scale (conformal) anomaly in field theories leads to new
anomalous transport effects that emerge in an external electromagnetic field in
an inhomogeneous gravitational background. In inflating geometry the QED scale
anomaly locally generates an electric current that flows in opposite direction
with respect to background electric field (the scale electric effect). In a
static spatially inhomogeneous gravitational background the dissipationless
electric current flows transversely both to the magnetic field axis and to the
gradient of the inhomogeneity (the scale magnetic effect). The anomalous
currents are proportional to the beta function of the theory.Comment: 6 pages, 2 figures; v2: clarifying remarks added, relation to the
Schwinger effect in de Sitter space discussed, published versio

### Free magnetized knots of parity-violating deconfined matter in heavy-ion collisions

We show that the local parity violation in the quark-gluon plasma supports
existence of free (meta)stable knots of deconfined hot quark matter stabilized
by superstrong magnetic fields. The magnetic field in the knots resembles the
spheromak plasma state of the magnetic confinement approach to nuclear fusion.
The size of the knot is quantized, being inversely proportional to the chiral
conductivity of the quark-gluon plasma. The parity symmetry is broken inside
the knot. Particles produced in the decays of the knots have unusual azimuthal
distribution and specific flavor content. We argue that these knots may be
created in noncentral heavy-ion collisions.Comment: 7 pages, 5 figures, RevTeX 4.

### Background magnetic field stabilizes QCD string against breaking

The confinement of quarks in hadrons occurs due to formation of QCD string.
At large separation between the quarks the QCD string breaks into pieces due to
light quark-antiquark pair creation. We argue that there exist a critical
background magnetic field e B ~ 16 m_\pi^2, above which the string breaking is
impossible in the transverse directions with respect to the axis of the
magnetic field. Thus, at strong enough magnetic field a new, asymmetrically
confining phase may form. The effect - which can potentially be tested at
LHC/ALICE experiment - leads to abundance of u-quark rich hadrons and to excess
of radially excited mesons in the noncentral heavy-ion collisions compared to
the central ones.Comment: 4 pages, 2 figures, uses RevTeX 4.

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